The present invention relates to a surface acoustic wave resonator of the type having an interdigital transducer on a piezoelectric substrate.
A Love wave type surface acoustic wave resonator will be described as a typical prior art example. There has been proposed a Love wave (SH wave) type surface acoustic wave resonator. In this case, an electro-mechanical coupling coefficient of a Love wave is far larger than that of a Rayleigh wave (P+SV wave) (see Japanese Pat. Pub. Disc. No. 260213/88).
In the Love wave type surface acoustic wave resonator the Rayleigh wave becomes a spurious mode, but as is wellknown in the art, even if other surface acoustic waves than the Love wave (the Rayleigh wave, for example) are used, a surface acoustic wave resonator can be formed by providing a large number of IDT electrodes on the piezoelectric substrate. In this instance, the Rayleigh wave is not a spurious mode, but the longitudinal mode and the transverse mode are still spurious ones as in the case of the Love wave type surface acoustic wave resonator.